“On the eve of the 50th anniversary of human kind’s first voyage to the Moon, a multinational crew returns to Earth after spending more than a half-year in space,” said NASA Public Affairs Officer Rob Navias during NASA TV coverage of the landing.

Prokopyev, Gerst and Aunon-Chancellor launched into orbit from Baikonur Cosmodrome in Kazakhstan on June 6, 2018. After spending two days catching up with the ISS, they docked with the Rassvet module to join NASA’s Drew Feustel and Ricky Arnold and Russia’s Oleg Artemyev as part of Expedition 56. When Feustel, Arnold and Artemyev returned to Earth on Oct. 4, 2018, Prokopyev, Aunon-Chancellor and Gerst formed the first part of Expedition 57.

Aunon-Chancellor, 42, and Prokopyev, 43, completed their first spaceflight. This was the second flight for 42-year-old Gerst, however, who now holds the record for the most cumulative days in space by a European Space Agency astronaut at 362 days.

Soyuz MS-09 pressure leak

In addition to conducting hundreds of science experiments, the trio oversaw multiple visiting vehicle arrivals and departures and had to deal with a minor leak aboard the space station, which originated from a hole on the Soyuz MS-09 spacecraft itself.

At about 7 p.m. EDT (23:00 GMT) Aug. 29, 2018, ground controllers in Houston and Moscow detected signs of a “minute pressure leak” somewhere in the orbiting complex. According to NASA, the pressure reduction was slow enough that it was decided to allow the crew to continue sleeping and address the issue once they woke up.

The two-millimeter-wide hole was found on the orbital module of the Soyuz MS-09 spacecraft. Photo Credit: NASA

“When the crew was awakened at its normal hour this morning, flight controllers at Mission Control in Houston and at the Russian Mission Control Center outside Moscow began working procedures to try to determine the location of the leak,” NASA said in a statement Aug. 30.

After discussions between the crew and mission control centers in Houston and Moscow, it was decided to have the cosmonauts apply an epoxy substance with medical gauze around the opening. Throughout the rest of the Soyuz MS-09 stay at the ISS, it showed no signs of further leakage.

The cause of the hole was thought to be caused by human hand, likely from someone who worked on the spacecraft on the ground. However, the exact circumstances are not yet known. Either way, the hole was on the Orbital Module of the Soyuz, which was not needed for re-entry. That being said, Roscosmos still wanted to examine and get a sample of the hole and epoxy used to seal it from the outside of the spacecraft.

That was to be done by spacewalking cosmonauts initially in November. However, the in-flight abort of the Soyuz MS-10 crew that was initially to join Expedition 57— NASA astronaut Nick Hague and Russian cosmonaut Aleksey Ovchinin — caused the outing to be pushed to Dec. 11, several days after Soyuz MS-11 launched with Russian cosmonaut Oleg Kononenko, NASA astronaut Anne McClain and Canadian Space Agency astronaut David Saint-Jacques.

During a 7 hour, 45 minute spacewalk Prokopyev and Kononenko used a knife to peel back thermal insulation in order to inspect the area of the Soyuz MS-09 spacecraft where the small leak occurred. This also involved using shears to cut away at the micrometeoroid shielding.

Returning home

When it finally came time for the crew to leave, Gerst handed command of the space station over to Kononenko, he along with McClain and Saint-Jacques will form Expedition 58. That handover occurred during a “change of command” ceremony on Dec. 18.

The next day at 5:30 p.m. EST (22:30 GMT), the departing trio said farewell to the soon-to-be Expedition 58 crew and the hatches between Soyuz and ISS were closed. Three hours later at 8:40 p.m. EST Dec. 19 (1:40 GMT Dec. 20), the spacecraft undocked from the Rassvet module.

A graphic of the Soyuz landing sequence. Image Credit: NASA

After two separations burns and three hours of coasting away from the space station, the Soyuz MS-09 performed its deorbit burn at 10:10 p.m. EST Dec. 19 (4:10 GMT Dec. 20). This 4 minute, 37 second burn slowed the vehicle down by 420 feet (128 meters) per second — just enough to lower its orbit enough to intersect with the atmosphere.

Just before this intersection — called entry interface — the three main parts of the spacecraft — the Orbital Module, Descent Module and Service Module — separated. Only the Descent Module with the crew inside is designed to survive re-entry.

During the re-entry process, the crew experienced a peak g-load of about 3.8 times that of normal Earth gravity for a brief period. Over about seven minutes, the spacecraft — protected by a heat shield — was slowed from about 5 miles (8 kilometers) per second to about 1.3 miles (2.2 kilometers) per second.

Once Soyuz was slow enough and deep enough in the atmosphere, a series of parachutes began to deploy, culminating with the main parachute for a several-minute slow descent to the ground.

While the spacecraft descended, the crew seats were pushed forward to better absorb the upcoming impact with the ground. Additionally, soft landing jets fired about a meter above the surface to cushion the landing further. Upon touchdown, the capsule landed in an upright position.

Within minutes, Russian search and rescue teams arrived and landed near the capsule to begin the recovery process. The three were pulled out one by one with Prokopyev emerging first, followed by Aunon-Chancellor and then Gerst.

The trio were placed in couches for a brief medical check. However, that didn’t last long as the cold temperatures prompted recovery teams to quickly move the three into a nearby inflatable medical tent.

After that, each crew member is expected to be transported to the nearby city of Dzhezkazgan, Kazakhstan. There, they will begin to part ways and head back to their respective home countries.

Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a blog about the International Space Station, called Orbital Velocity. He met with members of the SpaceFlight Insider team during the flight of a United Launch Alliance Atlas V 551 rocket with the MUOS-4 satellite. Richardson joined our team shortly thereafter.
His passion for space ignited when he watched Space Shuttle Discovery launch into space Oct. 29, 1998. Today, this fervor has accelerated toward orbit and shows no signs of slowing down. After dabbling in math and engineering courses in college, he soon realized his true calling was communicating to others about space. Since joining SpaceFlight Insider in 2015, Richardson has worked to increase the quality of our content, eventually becoming our managing editor. @TheSpaceWriter